Method for producing low alloy hot rolled steel strip or sheet having high tensile strength, low yield ratio and excellent total elongation

摘要

A method for producing a low alloy hot rolled steel strip or sheet comprising hot rolling a steel slab at a finishing temperature not higher than the Ar3 transformation temperature plus 60 DEG C. and cooling and coiling the hot rolled strip at a temperature not higher than 500 DEG C. The steel slab contains not more than 0.20% carbon, 0.50 to 2.50% manganese and 0.05 to 1.0% chromium and optionally contains not more than 1.0% silicon, the balance being iron and unavoidable impurities. The resultant strip or sheet has a high tensile strength of not less than 40 kg/mm2, a low yeild ratio of not more than 70% and an excellent total elongation of not less than 25%.